Vinylidene fluoride coating compositions containing polyimides

ABSTRACT

This disclosure concerns vinylidene fluoride polymer compositions containing a minor proportion of polyamide-acid resin which, after heat-curing of the composition, is converted to a polyimide resin. The coatings and films made from the cured composition have self-lubricating characteristics, improved wear resistance and impact resistance and better adhesion to substrates.

United States Paten King I 1 51 June 6, 1972 [54] VINYLIDENE FLUORIDECOATING 3,316,212 4/1967 Angelo ..260/857 P1 COMPOSITIONS CONTAINING3,356,759 12/1967 ..260/857 Pl 3,356,760 12/1967 ..260/857 PI POLYIMIDES7 3,391,221 7/1968 Gore ..260/857 PI [72] Inventor: James Ping King,Lansdale, Pa.

I Primary E.xaminerPaul Lieberman [73] Asslgnee: Pennwalt Corporation,Ph1ladelph1a, Pa. Atmmey Car1 A Hechmer Jr. and Stanley Litz [22] Filed:Jan. 27, 1971 [57] ABSTRACT 21 A LN 110258 1 pp 0 This disclosureconcerns vinylidene fluoride polymer compositions containing a minorproportion of polyamide-acid [52] US. Cl. ..260/857 PA, 1 17/124 E, 117/132 CF, resin which, after heat-curing of the composition, isconverted 1l7/138.8 B, 117/138.8,UF, 117/148, 117/161 P, to a polyimideresin. The coatings and films made from the 1 17/161 UN, 260/313 M,260/31 3 N, 260/313 F cured composition have self-lubricatingcharacteristics, im- 2 0 3 N, 2 0 32 0 31 8 N, 2 0 332 R, proved wearresistance and impact resistance and better adhe- 260/336 1: 260/37 Nsion to substrates. [51] Int. Cl ..C08g 41/04 [58] Field of Search..260/857 PI; 117/161 [56] References Cited 15 Claims, N0 Drawingsdichlorodifluoroethylene,

t e tr ac arboxylic acid dianhydride of the formula m The presentinvention relates to vinylidene fluoride polymer 1 coating compositions,cured films of said compositions, and i substrates coated with saidcured films. More particularly, this 1 invention concerns a vinylidenefluoride polymer composition 3 containing a minor proportion ofp'olyamide-acid resin, which subsequent heat-curing converts to apolyimide resin.

poorer than desired adhesiveness to the substrate. This inventionalleviatesthe foregoing'deficiencies by providing a modifiedpolyvinylidene fluoride resin composition having higher melting point,better solvents and chemicals resistance, j better adhesion tosubstrates, self-lubricating characteristics, and better wearresistance. The compositions may be applied to such substrates asmetals, e.g., steel, aluminum, copper,' brass, etc., glass and tofabrics made of natural or synthetic fibers. It is an advantage of theinvention that metal substrates, such as steel, do not require specialtreatment, for example, sandblasting, galvanizing or priming with epoxyresins, in order to obtain the desired level of adhesiveness thereto ofthe coatings embodied herein.

A brief but' comprehensive survey of polymerization techniques used inpreparing vinylidene fluoride polymers embodied in the composition ofthis invention is found in the specifications'of U.S. Pat. No,2,435,537to Ford et al., and U.S. Pat. No. 3,193,539 toM. Hauptschein.The terms vinylidene fluoride polymer" and polyvinylidene fluoride usedherein refer not only to the normally solid high molecular weightfilm-forming homopolymers of vinylidene fluoride, but A also thenormally solid high molecular weight, film-forming vinylidene fluoridecopolymers containing at least about .75

mol percent of vinylidene fluoride. Suitable comonomers are thehalogenated ethylenes such as sym.

l.-chlorol ,2,2-trifluoroethylene, tetrafluoroethylene,hexafluoropropene, vinyl fluoride, vinyl chloride and the like. When atleast about 75 mol percent of vinylidene fluoride is present, theimportant chemical resistance, resistance to the deteriorative effectsof the sun and weather, and mechanical characteristics of the copolymersof vinylidene fluoride are essentially the same as the ,homopolymer.These vinylidene fluoride polymers and' copolymers have softening pointsranging from about 120 C. to 180 C., the homopolymers generally havingthe higher softening temperatures. The primary particle sizes of theparticulate polyvinylidene fluoride in the coating formulations hereindescribed are, in general, within the range of about 0.05

micron to about 1 micron in diameter. However, these particles arepresent in the dispersions described below as agglomerates containingfrom 1 to about 35 primary particles,

preferably from 1 to particles peragglomerate.

One embodiment of the present invention is: (A) a filmformingcomposition comprised of a dispersion in organic liquid solvent ofvinylidene fluoride polymer, and in admixture in said solvent, apolyamide-acid component comprising the reaction product of an organicdiarnine and tetracarboxylic acid dianhydride, the proportion of thepolyamide-acid component to the vinylidene fluoride polymer being fromabout 10 to about 40 parts by weight, preferably from about to parts,per 100 parts by weight of vinylidene fluoride polymer. When thepolyamide-a'cid component exceeds about said 40 1 parts per 100 parts ofthe base resin, the impact strength of the cured compositions isconsiderably less than desired.

The polyamide-acid component is the well known precursor I of thepolyimide which is formed by exposure of the polyamide-acid to elevatedtemperatures. More specifically, the polyamide-acid is of a diamine ofthe formula H N-R' -NH where R is arylene (a divalent aromatic radical),and a O l NH- HOzC C 0:11

where R is a tetravalent organic radical. Preferably, R is selected fromthe group consisting of arylene radicals in metaphenylenediamine,paraphenylene-diamine, benzidine, 4,4'-diaminodiphenyl propane,4,4-diaminodiphenyl methane, 4,4'-diaminodiphenyl ether,4,4-diaminodiphenyl sulfone and 4,4'-diaminodiphenyl sulfide, and R isselected from the group consisting of aromatic radicals in pyromelliticdianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride,3,3,4,4'-diphenyl tetracarboxylic dianhydride, l,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'- diphenyl tetracarboxylicdianhydride, 2,2-bis(3,4-dicarboxyphenyl) propane dianhydride,bis(3,4-dicarboxyphenyl) sulfone dianhydride, 3,4,9,l0-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl' ether dianhydrideand 3,4,3, 4-benzophenone tetracarboxylic dianhydride. The formation ofsuch polyamide-acids (polyimide precursors) and their conversion intopolyimides by heating are described in the literature, for example, theKirk-Othrner Encyclopedia of Chemical Technology", 2nd edition, vol.-16, pg. 42; and U.S. Pat. Nos. 2,710,853, 3,356,759 and 3,356,760, andth als by ef9!!91vinastr 3&asaa

O 0 HzN- NHz ll 1] O/ \O m-phenylenedlarnlne pyromellitic anhydride ismlB2 polyamide-acid (precursor) The polyamide-acid compositions will ingeneral have a viscosity of the order of 10 to poises, preferably 60 90poises, measured as a 53 percent solution in a mixture of N-methylpyrollidone-xylene solvents by Brookfield viscometer Model LVF,Spindle No. 3, 12 rpm.

The usual method of utilizing the coating composition of this inventionis to prepare films or coatings on a substrate from a non-agueousdispersion of polyvinylidene fluoride in an organic latent solventcontaining in admixture the polyamideacid (polyimide precursor)component homogeneously mixed with the dispersion. A latent solvent isdefined in the art as an organic liquid having a boiling point (atatmospheric pressure) above about 50 C., preferably about 300 C., whichlidene fluoride polymer particles to coalesce. Representative latentsolvents include tetraethylurea, dimethyladipate, diethyladipate,diethylsuccinate, dimethylphthalate, diethylphthalate, diethyloxalate,triethylphosphate, diethylforrnamide, dimethylsebacate,dimethylsuccinate, propylene carbonate, ethylene carbonate, gammabutyrolacetone,2- nitropropane, acetone, 4-methoxy-4 methyl pentanone-Z,isophorone, methyl ethyl ketone, cyclohexanone, Z-methoxyethylacetate,2-butoxyethylacetate, 2-ethoxyethylacetate, diethylene glycol monoethylether acetate, hexylacetate, diacetone alcohol and others well known inthe art. In general, the quantity of the latent solvent in the polymericdispersion will be in the range of from about 80 to about 300 parts byweight per 100 parts by weight of polyvinylidene fluoride. Obviously,the viscosity of the polymeric dispersion is decreased as the relativeproportion of latent solvent therein increased. If desired, otherorganic volatile diluents which have no latent solvating action on thevinylidene fluoride polymer may be added to reduce the dispersionviscosity, to improve the flow characteristics, and to promote thewetting action of the latent solvent on the polymer powder. The amountof the volatile diluent may be as much as up to about 100 parts byweight per 100 parts of the polyvinylidene fluoride. Examples of suchnon-solvent diluents are xylene, toluene, diisobutylketone, N- methylpyrollidone, aliphatic naphthas, aromatic naphthas, methyl isobutylcarbinol and others well known in the art. The viscosity of thedispersion can be further reduced by adding from about 0.01 to about 2parts of a cationic surfactant per 100 parts by weight of dispersionsolids as disclosed in US. Pat. No. 3,441,531. Finely divided pigments(e.g., titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, etc.)and other particulate solids such as stainless steel powder or flakes,graphite powder, mica, and tungsten carbide may be included in thedispersions.

In order to impart even more lubricity to the coatings and filmsprepared from the described compositions, there can be mixed with thedispersion a minor proportion of particulate tetrafluoroethylene polymer(PTFE), i.e., from up to about 30 parts and preferably from about toabout 25 parts by weight per 100 parts by weight of the vinylidenefluoride polymer. The terms tetrafluoroethylene polymer andpolytetrafluorethylene (PTFE)" used herein mean not only the normallysolid high-molecular weight tetrafluoroethylene homopolymers (such asdescribed in US. Pat. No. 2,559,752) but also the normally solidhigh-molecular weight copolymers of tetrafluoroethylene containing apredominance of tetrafluoroethylene units, for example, with up to about30 mole percent of comonomers such as vinylidene fluoride, lchlorol-fluoroethylene, hexafluoropropene, trifluorochloroethylene and thelike, and also the lowermolecular weight tetrafluoroethylene polymersobtained by the pyrolysis of normally solid high-molecular weightpolytetrafluoroethylene such as described in US. Pat. Nos. 2,496,978 and2,978,519.

The aforesaid dispersions are conveniently prepared by mixing thepowdered vinylidene fluoride polymer, latent solvent, optional volatilesolvent, the polyamide-acid component, and optional pigments, othersolids and tetrafluoroethylene polymer, if desired, in a suitable mixingapparatus such as a paint mill, sand mill, ball mill, rod mill, or ahigh-shear blending unit. Well known techniques for laying down thecoating composition involve applying the dispersion by spraying or dipcoating, or by doctor blade or reverse roll coating to the substrate(e.g., metal, cloth, plastic, wood, glass, etc.). The coated material isinserted in an oven and dried and cured at from about 250 F. to about650 F. At these elevated temperatures conversion of the polyamide-acidprecursor to the polyimide takes place simultaneously with the fusionand curing of the matrix vinylidene fluoride polymer to leave a filmcomprised of this durable and compatible resinous mixture. Unsupportedfilms of the vinylidene fluoride polymer-polyimide mixture can beobtained by doctor blade coating the dispersion on apolytetrafluoroethylene sheet or PTFE-coated surface, followed by curingat 250 to 650 F., and, after cooling, removing the film from thenon-adherent substrate. Another method of preparing unsupported film isto coat a thin aluminum foil with the desired thickness, and afterheat-curing and cooling, removing the aluminum therefrom by immersion in20% HCl solution to dissolve the tin foil and leave the film, which isthen water-rinsed and dried.

In accordance with this invention, other embodiments of this inventionthus constitute: (B) a coated substrate prepared by mixing togethervinylidene fluoride polymer, a latent solvent, and a minor proportion ofa polyamide-acid to form a coating (film-forming) composition, coating asubstrate with said composition and heating the coating to produce adried and cured film on said substrate composed of a blend of about 10to 40 parts by weight, preferably 20 to 30 parts, ofa polyimide of apolyamide-acid having recurring units of the formula wherein the arrowsdenote isomerism, and wherein R is a tetravalent organic radical and Ris arylene as previously denoted, per parts by weight of vinylidenefluoride polymer; and (C) the resinous cured films thus produced,supported or unsupported. As previously mentioned, the polymer blend canoptionally contain up to about 30 parts by weight of tetrafluoroethylenepolymer, preferably 15 25 parts, per 100 parts by weight of vinylidenefluoride polymer, and other modifying solids such as pigments. Films andcoatings having thicknesses on the order of about 0.5 mil to 15 mils areprepared in the foregoing manner.

The excellent properties and advantages of the present compositions areillustrated by the following examples which are exemplary only andshould not be construed as limitative of the scope of the invention asdescribed and claimed herein. In the example all ingredients aremeasured in parts by weight and mixtures are defined by the weightpercents of their components.

EXAMPLE 1 parts of a representative polyimide precursor (polyamide-acid)composed of the recurring unit in a solvent mixture 134 parts) of amajor proportion of N- methylpyrrolidone and a minor proportion ofxylene (viscosity of 60 90 poises, Brookfield viscometer Model LVF,Spindle No. 3, l2 r.p.m.) is slowly mixed with a dispersion of450 partsof particulate polyvinylidene fluoride in 550 parts of a latent solventsmixture (4:1 weight ratio) of dimethyl phthalate and diisobutyl ketone(Kynar 202" vinylidene fluoride polymer, product of PennwaltCorporation). An additional 200 parts of this solvents mixture is addedto provide a dispersion containing 36,8% total non-volatiles (i.e.,resins).

The above-prepared dispersion is sprayed on cold-rolled steel, anodizedaluminum, untreated aluminum and SAE 4620 ring, and the coatings curedat 148 C. for 3 hours and then C. for 1 hour. Average dry film thicknessis 1.5 mils. The polyamide-acid component therein is thereby convertedto the polyimide of the recurring unit Impact resistari etTfThcGatingsonQQEFe mEasIred by 60 inch-pounds impact on aseven-eighth inch steelball, and the coatings neither rupture nor delaminate. A coated steelpanel is placed in a salt spraying chamber and a few blisters of number8 in size are observed after an extended period of eleven days. Pencilhardness of the coatings range between H and 3H. Contact angles withwater are between 70 and 90 Various organic solvents such as xylene,methylene chloride and methylethyl ketone have no effect on the coatingsafter 16 .hours of immersion. The coatings are also resistant to 35%EXAMPLE 2 A solution of 50 parts of the polyimide precursor employed inthe previous example in 90 parts of the same solvent is mixed with adispersion of 122 parts of the particulate polyvinylidene fluoride in148 parts of dimethyl phthalatediisobutyl ketone solvents mixtures, and50 parts of a 50 percent aqueous latex of high molecular weighttetrafluoroethylene polymer (Tetran 30PTFE, product of PennwaltCorporation). One hundred parts of the solvents mixture is added theretoto give a dispersion containing 36 percent total polymer constituents.

The dispersion is sprayed on SAE rings, anodized aluminum andcold-rolled steel panels, and the coatings are cured at 190 C. for lhour (dried film thickness-1 mil). Contact angles with water are between90 and 105.

Impact strength of the coated aluminum and cold-rolled steel panels .aremeasured by 60 inch-pounds impact on a seven-eighth inch steel ball, andthe coatings neither rupture nor delaminate. A coated steel panel isinscribed with crosshair lines and placed in a salt spraying chamber.There is no change in the coating after 7 days exceptnormal rustingalong the inscribed lines; however, rusting is propagating underneaththe coating along the inscribed lines after 13 days.

Average erosion rate of 1 mil coatings on SAE 4620 rings against RC30-27 blocks, as measured on the Alpha LFW-l Lubricant Tester is 0.033mils/min (72 RPM or 26 ft/min.)

' with the maximum load of 630 pounds. Average pressure at failure is44,000 psi. Static and dynamic coefficients of friction are 0.12 and0.07 to 0.13, respectively.

EXAMPLE 3 The procedure of Example 2 is repeated except that for thetetrafluoroethylene polymer (PTFE) latex in the dispersion issubstituted 30 parts of lower molecular weight tetrafluoroethylenepolymer (as obtained by pyrolysis of high molecular weight PTFEaccording to the procedure of US. Pat. No. 2,496,978) dispersed in 50parts dimethyl phthalate; this additive is a paste like PTFE dispersion.The vinylidene fluoride polymer/polyamide-acid/PTFE dispersion is usedto coat substrates as in the previous example, followed by heatcuring.The coated aluminum and steel panels are evaluated and found to haveproperties similar to those described in Example 2.

EXAMPLE 4 To a dispersion of 243 parts of the previously describedparticulate vinylidene fluoride polymer in 297 parts of mixed solvents(dimethyl phthalate and diisobutylketone, 4:1 weight ratio) are addedparts of the aforementioned polyamideacid (polyimide precursor) insolution with 90 parts N -methylpyrollidone and xylene solvents, 30parts additional N -methylpyrollidone, and 60 parts aqueouspolytetrafluoroethylene latex containing 50 percent PTFE (Tetran 30PTFE,product of Pennwalt Corporation) and 200 parts additionaldimethylphthalate-diisobutylketone solvents mixture.

The resulting dispersion (34 percent non-volatile content) is gentlyagitated for 10 minutes and then sprayed on SAE 4620 rings, anodizedaluminum and cold-rolled steel panels. The coated samples are firstcured at 80 C. for 1 hour and then C. for 50 minutes. The averagethickness of dried film on the coated panels is 1.5 mils and on the SAErings, 0.5 mil.

Impact resistances of the coated aluminum and steel panels are measuredby 60 inch-pounds impact on a seven-eighth inch steel ball, and thecoatings neither rupture nor delaminate. The average erosion rate of thecoated SAE rings against RC 30-27 blocks as measured on the Alpha LFW-lLubricant Tester with a speed of 72 RPM (26 ft/min.) at a maximum loadof 630 pounds is 0.0343 mils/min. The average pressure at failure is46,000 psi. Static and dynamic coefficients of friction are 0.10 and0.07 to 0.12, respectively. The results of salt spraying on a coatedpanel show very slight blistering along the inscribed lines after 6days.

I claim:

1. A film forming composition comprised of a dispersion in organicliquid solvent of vinylidene fluoride polymer containing at least about75 mol percent of vinylidene fluoride and in admixture in said solvent,at polyamide-acid of a diamine of the formula H N-R'-NH where R isarylene and a tetracarboxylic acid dianhydride of the formula where R isa tetravalent organic radical, the proportion of the polyamide-acidcomponent to the vinylidene fluoride polymer being from about 10 toabout 40 parts by weight per 100 parts by weight of vinylidene fluoridepolymer.

2. A composition according to claim 1 wherein the polyamide-acidcomponent is from about 20 to 30 parts per 100 parts of the vinylidenefluoride polymer.

3. A composition according to claim 1 wherein the dispersion contains inadmixture from 0 to about 30 parts by weight of tetrafluoroethylenepolymer per 100 parts by weight of vinylidene fluoride polymer.

4. A composition according to claim 3 wherein the amount oftetrafluoroethylene polymer is from about 15 to about 25 parts per 100parts of the vinylidene fluoride polymer.

5. A composition according to claim 1 where in the polyamide-acidcomponent R is selected from the group consisting of arylene radicals inmetaphenylenediamine, para-phenylenediamine, benzidine,4,4-diaminodiphenyl propane, 4,4- diaminodiphenyl methane,4,4-diaminodiphenyl ether, 4,4- diaminodiphenyl sulfone and4,4-diaminodiphenyl sulfide,

and R is selected from the group consisting of aromatic radicals inpyromellitic dianhydride, 2,3,6,7-naphthalene tetracarboxylicdianhydride, 3,3,4,4-diphenyl tetracarboxylic dian- 6. A coatedsubstrate prepared by mixing together finely-divided vinylidene fluoridepolymer containing at least about 75 mol percent of vinylidene fluoride,organic liquid solvent, and from about 10 to about 40 parts by weightper 100 parts by weight of the vinylidene fluoride polymer ofpolyamide-acid of a diamine of the formula l-l N-R'-Nl-l where R isarylene and a tetracarboxylic acid dianhydride of the formula where R isa tetravalent organic radical, to form a film-forming composition,coating a substrate with said composition and heating the coating toproduce a dried and cured film on said substrate composed of a blend ofthe vinylidene fluoride polymer and the polyimide of the polyamide-acidprecursor.

7. A substrate according to claim 6 wherein the polyimide component isfrom about 20 to 30 parts per 100 parts of the vinylidene fluoridepolymer.

8. A substrate according to claim 6 wherein the coating contains from toabout 30 parts by weight of tetrafluoroethylene polymer per 100 parts byweight of vinylidene fluoride polymer.

9. A substrate according to claim 8 wherein the amount oftetrafluoroethylene polymer is from about 15 to about 25 parts per 100parts of the vinylidene fluoride polymer.

10. A substrate according to claim 6 where the polyimide is derived froma polyamide-acid in which R is selected from the group consisting ofarylene radicals in metaphenylenediamine, para-phenylene-diamine,benzidine, 4,4- diaminodiphenyl propane, 4,4'-diaminodiphenyl methane,

4,4'-diaminodiphenyl ether, 4,4-diaminodiphenyl sulfone and4,4diaminodiphenyl sulfide, and R is selected from the group consistingof aromatic radicals in pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3,4,4'- diphenyl tetracarboxylicdianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride,2,23,3-diphenyl tetracarboxylic dianhydride,2,2-bis(3,4-dicarboxyphenyl) propane dianhydride,bis(3,4-dicarboxyphenyl) sulfone dianhydride,

3,4,9,10-perylene tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride and 3,4,3,4-benzophenone tetracarboxylic dianhydride.where R is a tetravalent organic radical.

12. A film according to claim 11 wherein the polyimide is from about 20to 30 parts per parts of the vinylidene fluoride polymer.

13. A film according to claim 11 containing from 0 to about 30 parts byweight of tetrafluoroethylene polymer per 100 parts by weight ofvinylidene fluoride polymer.

14. A film according to claim 13 wherein the amount oftetrafluoroethylene polymer is from about 15 to about 25 parts per 100parts of the vinylidene fluoride polymer.

15. A film according to claim 11 where the polyimide is derived from apolyamide-acid in which R is selected from the group consisting ofarylene radicals in metaphenylenediarnine, para-phenylene-diamine,benzidine, 4,4 diaminodiphenyl propane, 4,4-diaminodiphenyl methane,4,4-diaminodiphenyl ether, 4,4-diaminodiphenyl sulfone and4,4-diaminodiphenyl sulfide, and R is selected from the group consistingof aromatic radicals in pyromellitic dianhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3',4,4- diphenyl tetracarboxylicdianhydride, l,2,5,6-naphthalene tetracarboxylic dianhydride,2,2,3,3-diphenyl tetracarboxylic dianhydride,2,2-bis(3,4-dicarboxyphenyl) propane dianhydride, bis(3,4-dicarboxyphenyl )sulfone dianhydride, 3,4,9,l0-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydrideand 3,4,3',4-benzophenone tetracarboxylic dianhydride.

11. A resinous cured film comprised of a blend of 100 parts b wei htvinylidene fluoride polymer containing at least aboutmolpercentofvinylidene uoride and from aboutlO to about 40 parts byweight of a polyimide of a polyamide-acid of a diamine of the formula HN-R' -Nl-l where R is arylene and a tetracarboxylic acid dianhydride ofthe formula mg? UNITED STATE S PATENT OFFICE.

Y CERTIFICATE OF CORRECTION Patent No. 3,668, 193 Dated v June 6. 1972Inventofls) Tames Pincx King (Appln HnjRRL It is certified'that errorappears in the above-identified patent and that said Letters Patentare-hereby corrected as shown below:

Column 2, line 22, close parenthesis after "3,4-dicarboxypheriyl" beforeether Column 2, line 55, insert "polyamide" beneath chemical structure.

Column 3, line 16, insert "is" after "therein" and before "ether".Column 3, line 42, delete da sh at end of line after quote mark.

Column 4, line 6, "tin" should read thin Column 4, line 69, "38, shouldread 36. 8%

Claim 5, Column 6, line 7l insert "diphenyl tetracarboxylic dianhydride"after 2, 2' 3, 3' and before 2, 2-bis (3, 4-

Claim 10, Column 8, line 3, delete "where R is a tetrawalent organicradical" This phrase belongs after the chemical formula of claim ll.Claim 15 /Column 8, line 23, "6' naptholene should read 6 naptholene.

Claim ll, Column 8 is not in numerical order. Insert "where R is atetravalentorganic radical" after the chemical formula of this claim 11.

Signed and sealed this 6th day of March 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. A composition according to claim 1 wherein the polyamide-acidcomponent is from about 20 to 30 parts per 100 parts of the vinylidenefluoride polymer.
 3. A composition according to claim 1 wherein thedispersion contains in admixture from 0 to about 30 parts by weight oftetrafluoroethylene polymer per 100 parts by weight of vinylidenefluoride polymer.
 4. A composition according to claim 3 wherein theamount of tetrafluoroethylene polymer is from about 15 to about 25 partsper 100 parts of the vinylidene fluoride polymer.
 5. A compositionaccording to claim 1 where in the polyamide-acid component R'' isselected from the group consisting of arylene radicals inmetaphenylenediamine, para-phenylene-diamine, benzidine,4,4''-diaminodiphenyl propane, 4,4''-diaminodiphenyl methane,4,4''-diaminodiphenyl ether, 4,4''-diaminodiphenyl sulfone and4,4''-diaminodiphenyl sulfide, and R is selected from the groupconsisting of aromatic radicals in pyromellitic dianhydride,2,3,6,7-naphthalene tetracarboxylic dianhydride, 3, 3'',4,4''-diphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylicdianhydride, 2,2'',3,3''-diphenyl tetracarboxylic dianhydride,2,2-bis(3,4-dicarboxyphenyl) propane dianhydride,bis(3,4-dicarboxyphenyl) sulfone dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydrideand 3,4,3'',4''-benzophenone tetracarboxylic dianhydride.
 6. A coatedsubstrate prepared by mixing together finely-divided vinylidene fluoridepolymer containing at least about 75 mol percent of vinylidene fluoride,organic liquid solvent, and from about 10 to about 40 parts by weightper 100 parts by weight of the viNylidene fluoride polymer ofpolyamide-acid of a diamine of the formula H2N-R''-NH2 where R'' isarylene and a tetracarboxylic acid dianhydride of the formula
 7. Asubstrate according to claim 6 wherein the polyimide component is fromabout 20 to 30 parts per 100 parts of the vinylidene fluoride polymer.8. A substrate according to claim 6 wherein the coating contains from 0to about 30 parts by weight of tetrafluoroethylene polymer per 100 partsby weight of vinylidene fluoride polymer.
 9. A substrate according toclaim 8 wherein the amount of tetrafluoroethylene polymer is from about15 to about 25 parts per 100 parts of the vinylidene fluoride polymer.10. A substrate according to claim 6 where the polyimide is derived froma polyamide-acid in which R'' is selected from the group consisting ofarylene radicals in metaphenylenediamine, para-phenylene-diamine,benzidine, 4,4''-diaminodiphenyl propane, 4,4''-diaminodiphenyl methane,4,4''-diaminodiphenyl ether, 4,4''-diaminodiphenyl sulfone and4,4''diaminodiphenyl sulfide, and R is selected from the groupconsisting of aromatic radicals in pyromellitic dianhydride,2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3'',4,4''-diphenyltetracarboxylic dianhydride, 1,2, 5,6-naphthalene tetracarboxylicdianhydride, 2,2''3,3''-diphenyl tetracarboxylic dianhydride,2,2-bis(3,4-dicarboxyphenyl) propane dianhydride,bis(3,4-dicarboxyphenyl) sulfone dianhydride, 3,4,9, 10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydrideand 3,4,3'',4''-benzophenone tetracarboxylic dianhydride. where R is atetravalent organic radical.
 11. A resinous cured film comprised of ablend of 100 parts by weight vinylidene fluoride polymer containing atleast about 75 mol percent of vinylidene fluoride and from about 10 toabout 40 parts by weight of a polyimide of a polyamide-acid of a diamineof the formula H2N-R'' -NH2 where R'' is arylene and a tetracarboxylicacid dianhydride of the formula
 12. A film according to claim 11 whereinthe polyimide is from about 20 to 30 parts per 100 parts of thevinylidene fluoride polymer.
 13. A film according to claim 11 containingfrom 0 to about 30 parts by weight of tetrafluoroethylene polymer per100 parts by weight of vinylidene fluoride polymer.
 14. A film accordingto claim 13 wherein the amount of tetrafluoroethylene polymer is fromabout 15 to about 25 parts per 100 parts of the vinylidene fluoridepolymer.
 15. A film according to claim 11 where the polyimide is derivedfrom a polyamide-acid in which R'' is selected from the group consistingof arylene radicals in metaphenylenediamine, para-phenylene-diamine,benzidine, 4,4''-diaminodiphenyl propane, 4,4''-diaminodiphenyl methane,4,4''-diaminodiphenyl ether, 4,4''-diaminodiphenyl sulfone and4,4''-diaminodiphenyl sulfide, and R is selected from the groupconsisting of aromatic radicals in pyromellitic dianhydride2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3'',4,4''-diphenyltetracarboxylic dianhydride, 1,2, 5,6''-naphthalene tetracarboxylicdianhydride, 2,2'',3,3''-diphenyl tetracarboxylic dianhydride,2,2-bis(3,4-dicarboxyphenyl) propane dianhydride,bis(3,4-dicarboxyphenyl)sulfone dianhydride, 3,4,9, 10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydrideand 3,4,3'',4''-benzophenone tetracarboxylic dianhydride.